In the processing of petroleum hydrocarbons and feedstocks such as petroleum intermediates, and petrochemicals and petrochemical intermediates, e.g., gas, oils and reformer stocks, chlorinated hydrocarbons and olefin plant fluids the hydrocarbons are commonly heated to temperatures of 50° C. to 600° C. Exposure of the hydrocarbon liquids to these elevated temperatures can result in the formation of fouling deposits on the hydrocarbon processing equipment. In many processes, the deposits reduce the bore of conduits and vessels and impede process throughput, impair thermal transfer, and clog filter screens, valves and traps. In the case of heat exchange systems, the deposits form an insulating layer upon the available surfaces to restrict heat transfer and necessitate frequent shut-downs for cleaning. Moreover these deposits reduce throughput, which of course, results in a loss of capacity with a drastic effect in the yield of finish product. Accordingly, these deposits have caused considerable concern to the industry.
For example, in the production of vinyl chloride monomer (VCM), either ethylene, oxygen and HCl are reacted in an oxychlorination unit or ethylene and chlorine are reacted in a direct chlorination unit to produce ethylene dichloride (EDC) that is then processed in a cracking unit to form the VCM. The plant normally includes recycling facilities to recover residual EDC from the cracking unit and purification facilities used to purify EDC from recycle, oxychlorination and direct chlorination.
Serious fouling occurs in the various units handling the liquid EDC. For example, in the primary EDC recovery unit, fouling occurs in the distillation trays and the transfer facilities, especially the reboilers. Fouling is particularly serious in the liquid phase of EDC in the primary EDC recovery unit, heavies column and the vacuum column. It is not uncommon for the fouling to require plant shutdown after only a few months of operation.
The fouling is believed to be due to highly chlorinated and/or oxygenated polymeric materials which are incompatible in the EDC stream.
A method prevent fouling of equipment used in the manufacture of ethylene dichloride using acylated amines prepared by reacting a C2-C10 mono-olefin polymer substituted with a C4-C10 monounsaturated dicarboxylic acid derivative and a basic amine; oil-soluble magnesium alkyl aromatic sulfonate; and combinations thereof is disclosed in U.S. Pat. No. 5,110,997.